(PG) **

Director: Morgan Spurlock.

Cast: Niall Horan, Zayn Malik, Liam Payne, Harry Styles, Louis Tomlinson.

IT'S good to watch documentaries about things you know nothing about. You might learn something and have your horizons broadened.

So what did I learn watching this doco about a band whose music I've never heard, whose film clips I've never seen, whose members I wouldn't know if I bumped into them in the street?

Well, firstly, the five members of One Direction are "regular lads". This can't be stressed enough. I think they mention it about 20 times and the film is full of them being "regular lads". Just "regular lads" going fishing, going camping, causing mass hysteria at every turn, and playing in stadiums to 65,000 people.

Also, their lives are crazy. Their fans are crazy (but awesome). And the five lads are very lucky. All these things get repeated - and repeated - through out.

Unfortunately I didn't learn anything about their music, other than the fact that they play a deftly written and ludicrously catchy kind of pop music that's influenced by rock, but with all the dangerous rough edges bevelled off so its smooth and shiny and so inoffensive your mum will love it. Having said that, there is pop music out there that is a million times worse than what One Direction is making. All five of them have great voices and can sing well, and their fans love the songs so much it makes them cry.

But rarely do we get any idea of where this music springs from and what it means to Niall, Zayn, Liam, Harry and Louis, despite the fact they recorded an entire album while making this film. This is mentioned for about one minute, and we see a couple of the members in the studio with their producer/songwriter, and then it's back to showing these regular lads in their crazy, lucky lives.

This gets to the crux of the problem with This Is Us. Showing too much of them making an album would just remind the cynics how manufactured they are and would point out to the fans that those amazing sentiments and feelings they're singing about are written by a bunch of 40-year-old men with goatees.

This Is Us - and One Direction for that matter - thrives on being goofy, safely anarchic, up for a laugh, organic, real and regular. It's desperate to come across as all these things, but even if the five lads are like that, the doco still comes off as massively stage-managed. It wants us to forget they're the creation of a svengali and just think of them as a force of nature.

They probably are five lovely genuine boys who really do go camping by themselves (and a film crew) in Sweden in the middle of a tour and who really do mess about constantly and never bicker and argue, but the whole thing feels like shameless propaganda. The insight into the lads, their music and even their lives is minimal.

Having X Factor creator Simon Cowell remind us at the start of the film that he put the band together on a whim, that they were reasonably successful on X Factor and then he seems surprised that they became massive despite him probably pumping millions into promoting and recording them ... well that taints the whole thing a bit.

The boys boast about how they're not one of those boy bands with choreographed dance moves ... yet they have a choreographer. It's things like that which make This Is Us feel like a carefully planned, 90-minute ad for One Direction.

There is no conflict, no negatives, no problems, no drama. This would be fine if the doco didn't just become a slightly numbing loop of "song, travel, goofing around, song, travel, goofing around" and gave us something meaningful about who these five fellas are. Outside opinions on their success are kept to an absolute minimum.

What is good about This Is Us is the boys' enthusiasm is infectious, much like their music. It's hard to totally hate it when it seems like they're having so much fun.

But who cares what I think? "Directioners" will be lining up around the block to see this film. The screening I attended featured an ad for their forthcoming album before the movie started and even this drew excited squeals of delight.

For the fans, there's a lot to like. The concert footage looks great (and there's plenty of it) and there seems to be unnerving amount of footage of the boys without their shirts on (which also drew excited squeals of delight).

What little insight we get is fascinating but it just makes you want more than just endless goofing and touring and stage managed shenanigans. A bit when Zayn - "The Mysterious One" - buys a house for his mum is sweet, and there's an interesting moment when he talks about the "graffiti room" he has at his house.

But the interesting moments are all too fleeting. This Is Us is like a balloon - it's shiny and kinda fun for about 10 minutes, but ultimately it's full of nothing.